There is a growing need for the real-time detection, classification and identification of airborne biological and non-biological particles for indoor and outdoor air quality monitoring, pulmonary patient monitoring, contagious person and animal monitoring, and for the early detection of deliberate releases of harmful aerosols such as from acts of terror or as an offensive military action.
In numerous indoor and outdoor environments there are aerosols that pose a health threat to humans. Harmful aerosols can come from numerous sources both natural and anthropogenic. The ability to monitor for the presence of such aerosols can provide a means to minimize exposure, as aerosols used as an act of terror or for offensive military use the impact can be lethal. Such harmful or lethal aerosols include types that are biological, chemical and radiological in nature.
Specific applications that require a real-time biological warning capability include battlefield defense, perimeter protection of mission critical facilities and building complexes such as military bases, facility protection against both indoor and outdoor aerosol attacks, mail biohazard screening, occupational hygiene monitoring, indoor air quality monitoring, patient monitoring of respiratory infections, etc. For each of these applications, a varied and complicated aerosol background is encountered making it a challenging problem to detect and discriminate a biological aerosol of interest from the commonly encountered aerosols for each application. Present state-of-the-art, real-time biological point detection involves sensing the auto-fluorescence of biological particulates via the excitation and detection of endogenous fluorophores and by measuring the elastic scattering of particles and/or its aerodynamic diameter using aerosol time-of-flight techniques. Techniques surrounding the extraction of auto-fluorescence, elastic scatter, and aerosol time-of-flight information from individual airborne particles are the most sensitive real-time techniques currently available. See U.S. Pat. Nos. 6,194,731; 5,999,250; 5,895,922; 5,701,012; 6,653,067; US Publication Nos. US20030223063; US20040125371; U.S. Pat. No. 6,885,440; and US Utility patent application Ser. No. 10/834,537.
The primary limitations of some known biological aerosol detection methods include the difficulty or inability in detecting airborne particulates that contain low concentrations of intrinsic fluorophores, and to discriminate from fluorescing background aerosols.
U.S. Pat. No. 6,885,440 discloses a method and apparatus for biological particle detection and classification using Mie scattering techniques and auto-fluorescence through the use of a single continuous wave laser or a laser with a modulation frequency of 50 MHz or greater. This commonly-owned patent is incorporated by reference in its entirety as if made a part of this present application.
U.S. patent application Ser. No. 10/834,537, filed Apr. 29, 2004 discloses a method and apparatus for biological particle detection and classification using elastic scattering, auto-fluorescence, and complex refractive index detection techniques through the use of one or more single continuous wave lasers and/or lasers with a modulation frequency of 20 MHz or greater. This application is incorporated by reference in its entirety as if made a part of this present application.
Therefore, a need exists for improved methods for detecting airborne biological and non-biological particulates, and for discriminating specific biological and non-biological particulates from commonly encountered background particulates.